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Translation of abstract (English)

A 3D radial k-space acquisition technique with homogenous distribution of the sampling density (DA-3D-RAD) is presented. This technique enables short echo times (TE < 0,5 ms), that are necessary for 23Na-MRI, and provides a high SNR-efficiency. The gradients of the DA-3D-RAD-sequence are designed such that the average sampling density in each spherical shell of k-space is constant. The DA-3D-RAD-sequence provides 34% more SNR than a conventional 3D radial sequence (3D-RAD) if T2*-decay is neglected. This SNR-gain is enhanced if T2*-decay is present, so a 1,5 to 1,8 fold higher SNR is measured in brain tissue with the DA-3D-RAD-sequence. Simulations and experimental measurements show that the DA-3D-RAD sequence yields a better resolution in the presence of T2*-decay and less image artefacts when B0-inhomogeneities exist. Using the developed sequence, T1-, T2*- and Inversion-Recovery-23Na-image contrasts were acquired for several organs and 23Na-relaxation times were measured (brain tissue: T1 = 29,0 ± 0,3 ms; T2* = 4 ms; T2l* = 31 ms; cerebrospinal fluid: T1 = 58,1 ± 0,6 ms; T2* = 55 ± 3 ms (B0 = 3 T)). T1- und T2*-relaxation times of cerebrospinal fluid are independent of the selected magnetic field strength (B0 = 3T/7 T), whereas the relaxation times of brain tissue increase with field strength. Furthermore, 23Na-signals of oedemata were suppressed in patients and thus signals from different tissue compartments were selectively measured.